Updates Dockerfile to recompose layers; use modern install practices

Dockerfile

@@ -21,7 +21,7 @@ COPY . .
 RUN make test && make
 
 
-FROM debian:10
+FROM debian:12
 
 RUN \
     apt-get update && \
@@ -38,28 +38,39 @@ RUN \
         software-properties-common && \
     apt-get clean
 
-# Kubectl
-RUN curl -fsS https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
-RUN echo "deb https://apt.kubernetes.io/ kubernetes-xenial main" | tee -a /etc/apt/sources.list.d/kubernetes.list
-
-# Packer
-RUN curl -fsS https://apt.releases.hashicorp.com/gpg | apt-key add -
-RUN apt-add-repository "deb [arch=amd64] https://apt.releases.hashicorp.com $(lsb_release -cs) main"
-
 # Docker
-RUN curl -fsS https://download.docker.com/linux/debian/gpg | apt-key add -
-RUN add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian $(lsb_release -cs) stable"
-
 RUN \
+    install -m 0755 -d /etc/apt/keyrings && \
+    curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc && \
+    chmod a+r /etc/apt/keyrings/docker.asc && \
+    echo \
+        "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian \
+        $(. /etc/os-release && echo "$VERSION_CODENAME") stable" > /etc/apt/sources.list.d/docker.list && \
     apt-get update && \
     apt-get install -y \
-        containerd.io \
         docker-ce \
         docker-ce-cli \
-        kubectl \
-        packer && \
+        containerd.io && \
+    apt-get clean
+
+# Packer
+RUN \
+    curl -fsS https://apt.releases.hashicorp.com/gpg | apt-key add - && \
+    apt-add-repository "deb [arch=amd64] https://apt.releases.hashicorp.com $(lsb_release -cs) main" && \
+    apt-get update && \
+    apt-get install -y packer && \
     apt-get clean
 
+# Kubectl
+ARG KUBERNETES_VERSION=v1.32.1
+
+RUN \
+    ARCH="amd64" && \
+    curl -fsSL "https://dl.k8s.io/release/${KUBERNETES_VERSION}/bin/linux/${ARCH}/kubectl" -o /usr/bin/kubectl && \
+    curl -fsSL "https://dl.k8s.io/release/${KUBERNETES_VERSION}/bin/linux/${ARCH}/kubeadm" -o /usr/bin/kubeadm && \
+    curl -fsSL "https://dl.k8s.io/release/${KUBERNETES_VERSION}/bin/linux/${ARCH}/kubelet" -o /usr/bin/kubelet && \
+    chmod +x /usr/bin/kubeadm /usr/bin/kubelet /usr/bin/kubectl
+
 COPY --from=builder /app/build/hope /usr/bin/hope
 
 VOLUME ["/src"]